Depending on the type of radiation used, it may be necessary to maintain a particular distance between the transducer or transducers and the surface of the test specimen. Furthermore, depending on the type of radiation used, it may be necessary to maintain a particular angle with respect to the surface of the test specimen. At least one pivoting system which can rotate the transducer or transducers about one or more pivot axes/rotation points is needed for this purpose in the case of curved surfaces, for example hemispherical ends of a rod.
Mechanical tolerances of the transducers themselves or those which occur when installing the transducers mean that a beam emitted by the transducers, for example an ultrasound beam, does not fall through the desired target point. One example of such a desired target point is the rotation point of the pivoting system. However, in terms of design, another rotation point which is not on the sound beam can also be selected for the pivoting system, and correspondingly displaced positioning (according to the design offset) can be carried out during pivoting. In this case too, the tolerances reduce the accuracy and prevent testing. The impingement point of the radiation is changed as a result even if, for example, only one of the pivot axes of the pivoting system is actuated. This reduces the accuracy of the materials testing or the materials testing is even made impossible.
In order to avoid this problem, it is known practice to insert the transducers into holders which are in mechanical contact with the surface of the test specimen. Runners or rollers ensure that the transducers follow the surface of the test specimen during movement and thus ensure the distance and angle. However, a prerequisite is that the curvature of the test specimen surface changes only slowly so that the mechanical system can follow the surface in a sufficiently accurate manner. However, the disadvantage of this solution is that the test specimen is exposed to a mechanical load. Furthermore, a certain amount of wear of the surface of the test specimen and a limited speed of the movement of the transducers result.